翼尖小翼近地效應之實驗與數值模擬分析

A joint Experimental and Numerical Study of Winglets in Ground Effect

郭彥良(Yen-Liang Kuo)

指導教授 ： 朱錦洲

共同指導教授 ： 張建成(Chien-Cheng Chang)

國立臺灣大學/工學院/應用力學研究所/碩士(2018年)

https://doi.org/10.6342/NTU201804118

摘要

翼尖小翼對於近地效應的影響於本研究中進行探討。利用水洞模擬帶翼尖小翼的半翼展機翼之下降過程，並且以動態與靜態量測其受力情形，而實驗目的為在近地效應下，比較傾斜角為0°、15°、30°、45°、60°、75°以及90°的翼尖小翼之升力曲線差異。近地效應（ground effect）又可分為靜態近地效應（static ground effect）與動態靜地效應（dynamic ground effect）。結果表明在雷諾數為5000或10000時，且不論在靜態近地效應（SGE）與動態靜地效應（DGE）下由實驗結果可知，SGE與DGE中的升力係數CL會隨攻角α的增大而增加；而當h <0.5c時，SGE與DGE的CL隨著與地面之高度h的減小而顯著增加。除此之外，機翼攻角較低時，在DGE中的升力係數CL曲線與相同攻角下的SGE幾乎差不多；然而，當攻角α過高時，DGE的升力明顯大於具有相同攻角SGE的升力。實驗結果也顯示，不論SGE與DGE，傾斜角為30°的翼尖小翼能產生更多的升力，而傾斜角為75°的機翼，則具有不錯的升力提升效果。在雷諾數5000下，ϕ=45°時，SGE的提升率會大於DGE的提升率；雷諾數10000，α≤15°時，DGE的升力提升率幾乎會大於SGE的提升率；然而，α≥20°時，則是DGE的升力提升率會小於SGE的提升率。本研究也針對展弦比進行近地效應的研究，發現不論攻角是6°、8°還是10°，展弦比1.5的升力提升效果會比展弦比2的高。最後藉由全翼展機翼的數值模擬來驗證半翼展機翼水洞實驗之結果，並發現二者結果相當吻合。

關鍵字

近地效應 ； 翼尖小翼 ； 傾斜角 ； 水洞實驗

並列摘要

In this study, the effect of the winglets is investigated in ground effect. The landing process of a rectangular semi-span wing with winglet is under static and dynamic force measurements in water tunnel experiments. The experimental analysis is aimed to compare the performance of winglet at cant angles 0°, 15°, 30°, 45°, 60°, 75° and 90° at various angles of attack. The flow over a wing with winglet in static ground effect (SGE) and dynamic ground effect (DGE) is studied. The results show that the lift coefficient CL in both SGE and DGE increases with increasing angles of attack α. It is also found that CL in SGE and DGE case significantly increases with decreasing ride height when h<0.5c. Additionally, when the wing at low-to-moderate angles of attack, the CL curve with ride height in DGE is almost the same as that in SGE for the same angle of attack. However, when α is high, the lift in DGE is evidently larger than that in SGE with the same angle of attack. The winglets of cant angle 30° produce more lift in DGE and SGE. The winglets at cant angle 75° produce the more lift-increasing effect. When cant angle ϕ is 45°, the lift-increasing rate in SGE will be greater than that in DGE at Reynolds number 5000. At low-to-moderate angles of attack, the lift-increasing rate in DGE will be almost higher than that of SGE at Reynolds number 10000. At high angles of attack, the lift-increasing rate in DGE will be less than that of SGE at Reynolds number 10000. The effect of the semi-span aspect ratio is also investigated in this study, and the results show that the lift improvement effect of the semi-span aspect ratio of 1.5 is higher than that of semi-span the aspect ratio 2 at low angles of attack. Finally, the experimental results are validated with numerical simulation of the full-span wing, and both results are quite consistent.

並列關鍵字

ground effect ； winglets ； cant angles ； water tunnel experiment

參考文獻

Ahmed, M. R., Takasaki, T., & Kohama, Y. (2007). Aerodynamics of a NACA4412 airfoil in ground effect. AIAA journal, 45(1), 37-47.

Anderson Jr, J. D. (2010). Fundamentals of aerodynamics: Tata McGraw-Hill Education.

Barber, T. (2006). Aerodynamic ground effect: a case study of the integration of CFD and experiments. International Journal of Vehicle Design, 40(4), 299-316.

Beechook, A., & Wang, J. (2013). Aerodynamic analysis of variable cant angle winglets for improved aircraft performance. Paper presented at the Automation and Computing (ICAC), 2013 19th International Conference on.

Chang, C.-c. (1992). Potential flow and forces for incompressible viscous flow. Proc. R. Soc. Lond. A, 437(1901), 517-525.